Magnetic saturation control devices



Oct. 23, 1962 H. J. M CREARY MAGNETIC SATURATION CONTROL DEVICES Original Filed Aug. 18, 1958 3 Sheets-Sheet l INVENTOR. HAROLD J M0 CREARY ATTY.

Oct. 23, 1962 H. J. MCCREARY 3,060,412

MAGNETIC SATURATION CONTROL DEVICES Original Filed Aug. 18, 1958 3 Sheets-Sheet 2 FIG. 5

s3 s2 SI INVENTOR. HAROLD J. M CREARY ATTY.

Oct. 23, 1962 H. J. M CREARY 3,060,412

MAGNETIC SATURATION CONTROL DEVICES Original Filed Aug. 18, 1958 3 Sheets-Sheet 3 INVENTOR.

HAROLD J. M CREARY ATTY.

United States Patent Claims. (Cl. 340174) This invention relates in general to magnetic control devices, and in particular to magnetic control devices which utilize local saturation for effecting their control function. This application is a division of the copending application of Harold J. McCreary, Serial No. 755,452, filed August 18, 1958, now Patent No. 3,014,988.

In magnetic circuits the quantity of magnetomotive force required to produce a flux of given magnitude is dependent upon the reluctance of the magnetic path. This reluctance is in turn dependent upon the length and cross sectional area of the path and the permeability of the core material. Once the magnetic material has been saturated a much greater percentage increase in magnetomotive force is required to produce a given increase in flux. Saturation of the magnetic material results in an increase in the reluctance of the magnetic circuit because of the decrease in the permeability of the magnetic material.

It is well known that if a magnetic core with a closed path has a gap cut in the core, the reluctance will increase to some higher value. This is the result of the air in the gap having a higher reluctance, or a lower permeability, than the iron. A similar result may be achieved by introducing a thin section of saturated magnetic material into the path. This in efiect is what the subject of the present invention accomplishes.

I have found that by passing sufiicient current through a wire, which has been inserted in a magnetic core at right angles to the normal flux in that core, to cause local saturation of a portion ofthe core in the immediate proximity to the wire, that the reluctance of the core will increase slightly. By increasing the number of turns of wire in the core, that is, by winding it in a manner shown in the various embodiments of the invention, this effect can be greatly increased. Moreover, if this winding is surrounded by its own core of highly permeable magnetic material, the power requirements of the control winding are greatly reduced. In this respect the magnetic saturation control element readily lends itself to low power control applications. Additionally, the control winding can be wound in a manner such that it will have substantially no mutual inductance with respect to the other windings coupled to the magnetic circuit. This condition is desirable in preventing feedback from the output circuit to the control circuit.

Accordingly, it is an object or" this invention to provide a novel means whereby the mutual inductance between a number of windings may be varied in a predetermined manner.

Another object of the invention is to provide means for switching magnetic flux from one path to another path.

A still further object of the invention is to provide means for selectively coupling a number of windings in a magnetic circuit to the exclusion of the remaining windings.

Still another object of the invention is to provide a novel telephone switch for magnetically connecting subscrib er stations.

A still further object of the invention is to provide a novel telephone conference circuit arrangement, where- 3,060,412 Patented Oct. 23., 1962 by one or more parties may be interconnected by magnetic means.

Another object of the invention is to provide a novel magnetic circuit wherein the magnetic flux traversing portions of a magnetic core may be selectively shunted through a plurality of individual core sections extending from said portions.

Another object of the invention is to provide a novel magnetic switching device of the shunt type employing saturation control elements which utilize a minimum of the more expensive high permeability magnetic materials.

Still another object of the invention is to provide a novel magnetic switching device using a saturation control element which may be rendered substantially independent of any flux variation in the core.

A further object of the invention is to provide a novel magnetic switching device using a magnetic saturation control element which can be readily inserted in an air gap in the magnetic core to produce a controlling function.

With the foregoing objects in view the principal feature of this invention consists in a magnetic circuit having a common core section with a plurality of distinct core sections extending peripherally therefrom in mutually separate loops, and with means for selectively saturating segments of the common core section whereby the magnetic flux in the common core section is diverted through selected ones of the distinct core sections.

Other objects and features of the invention will be come apparent upon a reading of the specification taken in conjunction with the following drawings:

FIG. 1 depicts one form of a magnetic saturation control element for use in a magnetic device of the general type shown in FIG. 6.

FIG. 2 shows another form of a magnetic saturation control element for use in a magnetic device of the general type shown in FIG. 6.

FIG. 3 shows a third form of a magnetic saturation control element for use in a magnetic device of the general type shown in FIG. 6.

FIG. 4 illustrates in schematic form the principle of magnetic saturation control applied to shunt-type magnetic circuits as used in the persent invention. In the showing of FIG. 4 it is assumed that the saturation control is effected by a winding disposed in a plane parallel to the main magnetic flux, which traverses the shunt leg, so that the saturation control flux is orthogonal to the first-mentioned flux.

FIG. 5 illustrates a magnetic switch according to the invention for selectively connecting a circuit to one of a plurality of other circuits.

FIG. 6 illustrates another magnetic switch according to the invention for selectively connecting a number of circuits together such as in a telephone conference circuit.

Any of the magnetic saturation control elements shown in FIGS. l-3 of the drawings may be interposed in a magnetic circuit, such as the central core section of the magnetic structure disclosed in FIG. 6, whereby the operation of the saturation control element substantially prevents the passage of the magnetic flux. FIG. 4 illustrates the concept, used in the present invention, of diverting the magnetic flux through an alternative path, i.e. one that shunts part of the magnetic circuit, upon energization of a local saturating control.

The construction and operation of the magnetic saturation control elements will first be described in detail with reference to the accompanying drawings.

Referring now to FIG. 1 of the drawings, one form of the magnetic saturation is shown. The magnetic circuit consists of a core 1 having legs 2 and 3, on the latter of which windings 4 and 5 are wound. Control core 6,

which lies in a plane perpendicular to leg 2 intersects leg 2 as shown. Leg 2 has two parallel rows of apertures 7a -7g lying substantially along the lines of intersection of control core 6 and leg 2. Control winding 8 is threaded through these apertures 7a-7h as follows: beginning at point 9 of the winding, it is threaded forwardly through aperture 7a, then downwardly and rearwardly through aperture 7b, then upwardly and forwardly through aperture 7c, and in like manner through the remaining apertures and terminating at point 10 of the winding.

Asusme that upon the energization of winding 4 a flux 1 will flow as shown. The magnitude of this flux is dependent upon the potential impressed upon, and the number of turns in, winding 4, and the reluctance of the magnetic circuit. Assume now that control winding 8 is energized to cause a flux 2 to flow as shown. This flux will cross flux 1 substantially along the lines of intersection of control core 6 and leg 2. Assuming further that the flux 2 is of sufiicient magnitude to saturate the portion of leg 2 which it traverses, it can be seen that the flux will encounter at the intersection of control core 6 and leg 2 a sheet of saturated magnetic material. In effect then, flux 1 encounters a path of very high reluctance in this portion of leg 2. As the reluctance of the magnetic circuit has been increased, 1 must decrease. Likewise, the mutual inductance between windings 4 and 5 will be varied as the reluctance of the magnetic circuit linking these windings is varied. It can be seen that the addition of the magnetic saturation control element to a conventional magnetic core results in variations in the reluctance of the magnetic circuit which are responsive to changes in the potential impressed upon the magnetic control element winding.

While special magnetic materials are not essential to the operation of the magnetic saturation control element, it can easily be seen that high permeability materials will enhance the controlling effect. It will also be noted that the mutual inductance between control winding 8 and windings 4 and 5 is very small due to the fact that the turns of control winding 8 lie substantially parallel to the path of flux 1. In this connection, it is to be noted that the control winding 8 may be wound on the control core 6, instead of being threaded through apertures 7a-7h in the main core, and produces similar saturation control results.

In FIG. 2 another form of the magnetic saturation control element is shown having a magnetic core 11, with legs 12 and 13, with windings 14 and 15 wound on leg 13. Leg 12 has a series of apertures 16a-16g through which magnetic control winding 17 is threaded. The manner of threading the windings through these apertures is apparent from a perusal of FIG. 2.

Assume current is caused to flow in control winding 17 from point 18 to point 19. A clockwise flux will be established around the portion of winding 17 lying in aperture 1611. Likewise a counter-clockwise flux will be established around the portion of the winding in aperture 16b, a clockwise flux around the portion in aperture 160, etc. A fiux pattern, having alternate positive and negative maxima between adjacent apertures, will result. It should be noted that, so far as windings 14 and 15 are concerned, the efiects of the oppositely directed fluxes generated by control winding 17 tend to cancel. Hence, for practical purposes, control winding 17 is non-inductive to windings 14 and 15. However, the local fluxes do exist and tend to saturate the portions of the core which they traverse, thus increasing the reluctance of the core. This change in reluctance of the core results in a variation in the mutual inductance between winding 14 and Winding 15. If the current in the control winding is varied, the mutual inductance between windings on the core will be varied accordingly.

In FIG. 3 there is shown another form of a magnetic saturation control element comprising a magnetic core 21 having legs 22, a, and 25b. The legs 25a and 25b are separated by an air gap 26. Windings 23 and 24 are wound on leg 22. In this embodiment the magnetic saturation control element has its own core which is inserted in the air gap 26 in close fitting relationship with legs 25a and 25b. This control core consists of parallel rows of stacked rectangular shaped pieces of magnetic material 27a to 27 with apertures in their centers. The control winding 29 is threaded through the control core as follows: beginning at point 30 of the winding, it passes rearwardly through the apertures of the parallel row of stacked rectangular pieces of material beginning with piece 27a, then to the right to the second adjacent parallel row of stacked rectangular shaped pieces of material and forwardly emerging at 270, then to the right and rearwardly to 272, then to the right and forwardly emerging at 27 then to the left and rearwardly to 27d, then to the left and forwardly emerging at 2712 and terminating at point 3-1.

It can be seen that control winding 29 is wound in bifilar fashion which renders it completely non-inductive to windings 23 and 24. In this embodiment it is preferable that the control core be fabricated of extremely high permeability material, such as Supermalloy. Since only a very small portion of the core need be of this type material, it would prove economical to do so. The stacking and lamina-ting of the magnetic material tends to reduce eddy current losses, but the device will operate satisfactorily even if the core is solid. With the use of high permeability materials a small voltage impressed across the control Winding 29 will quickly saturate the control core and hence a relatively small control signal may be utilized.

In FIG. 4 is shown the principle of magnetic saturation control applied to shunt-type magnetic circuits as used in the instant invention. This figure shows a magnetic core 46 with two large circular apertures and three legs 41, 42, and 43 having Windings 44 and 45 wound on legs 41 and 43 respectively. There are two small apertures 46 and 47 in leg 42 through which magnetic control winding 48 is threaded. The control winding 48 is so disposed that its flux will not transverse legs 41 and 43 but remain in a local path in leg 42. It will be noted that in the saturation control arrangement specifically shown in FIG. 4, a saturation control winding is provided which is disposed in a plane parallel to the magnetic flux due to the winding 44 or 45, which traverses shunt leg 42 so that the saturation control flux is orthogonal to the first-mentioned flux.

Normally winding 44 is in non-inductive relationship with winding 45 since the flux path containing legs 41 and 42 is shorter than the flux path containing legs 41 and 43. Consequently the reluctance of the former path will be less than that of the latter. Hence, any flux set up by either winding 44 or winding 45 will prefer the short path through leg 42. However, if a current suflicient to cause saturation is passed through control winding 48, the reluctance of leg 42 will be greatly increased and any flux emanating from either winding 44 or winding 45 will now prefer the longer path consisting of legs 41 and 43. It can be seen then that by saturating leg 42 windings 44 and 45 can be switched into inductive relationship with each other. Here again no special magnetic materials are required, but the use of high permeability material is desirable. Since the embodiment shown in FIG. 4 may be made extremely small, the use of these expensive high permeability materials can be economically justified.

It will be understood that the magnetic circuits shown in FIGS. 1-4 inclusive are merely for the purposes of illustration and are not intended to limit the scope of the invention. In addition, aperture sizes, spacings, and number of turns on the control windings are employed for clarity of illustration only and should not be construed to limit the invention in these particulars.

FIG. 5 shows a novel telephone connector switch using magnetic saturation control. This magnetic switching device, generally speaking, utilizes the magnetic circuit concept illustrated in 4 except that the satura tion control winding of FIG. 4 is replaced by a permanent magnet control. The structure consists of a magnetic core 200 which is comprised of a relatively large ring type core section 201, to the periphery of which are attached numerous smaller ring type core sections 202.- Associated with each of. these smaller ring type core sec tions 202 are windings 203 which are connected to individual subscriber stations, only a few of which are shown.

A stepping switch mechanism 210 of conventional design is comprised of motor magnet 211 and armature 212 which is connected to pawl 213, which engages ratchet 214 carrying arm 215, to which magnet 216 is attached. The means for energizing the motor magnet 211 are not shown.

It will be noted that the-re are no control windings associated with this embodiment, the saturating effect being produced by the magnet 216. The magnet 216 may be of either the permanent or electric type. Preferably it is U-shaped and adapted to straddle the core section 201. A calling line is connected over leads 220 to winding 204 which is coupled to magnetic core section 201. Normally, with the magnet 216 resting at its home position opposite subscriber station S1, the path of any flux in the circuit will be through the small core section 202 associated with subscriber station S1 and the large core section 201.

In this device, subscriber station S1 is normally magnetically coupled to core section 201 and therefore inductively coupled to winding 204. Assuming that it is desired to couple subscriber station S6 to winding 204, the stepping switch 210 is operated to step the magnet 216 around until it rests substantially over the line of intersection of the core section 202 associated with subscriber station S6 and the core section 201, substantially as shown in the drawing. In this position, subscriber station S6, via its winding 203, is magnetically coupled to winding 204 while the other subscriber stations remain effectively disconnected from the magnetic circuit. This is so because magnetic flux tends to take the path of least reluctance, which, in this case, is normally through core section 201. But, upon encountering a saturated portion of core section 201 such as that which now exists at the intersection of the core section 202 associated with subscriber station S6 and core section 201, the flux flows along the path of lower reluctance around the saturated portion, which is through said core section 202 associated with subscriber station S6. Hence, subscriber station S6 is inductively coupled to winding 204. In like manner any other subscriber station may be coupled to winding 204 to the exclusion of all the remaining stations by selective operation of stepping switch 210.

In FIG. 6 is shown a telephone conference circuit arrangement utilizing magnetic saturation control elements. A magnetic core 300 similar to that shown in FIG. is comprised of large core section 301 and a plurality of smaller core sections 302. Associated with each of these smaller core sections 302 are windings 303 which terminate in subscriber stations. Again, for the purposes of clarity, only a few of the subscriber stations are shown. Additionally, a series of pairs of apertures 304, through which individual magnetic control windings 305, schematically indicated in FIG. 6, are provided. These saturation control windings lie substantially in the area of intersection of the core sections 302 with the core section 301. The saturation control windings may, for example, be of the form shown in FIG. 4, that is, they may be disposed in a plane parallel to that of the flux traversing large core section 301. As disclosed previously the saturation control elements shown in FIGS. 1-3 may be used instead, as schematically indicated by way of example for core sections 302A, 302B, and 302C in FIG; 6. Thus, referring to these three core sections, respectively, saturation may be effected by a control winding 305, FIG. 6, of an element corresponding to that shown in detail in FIG. 2; or it may 'be efiected by an arrangement, such as shown in detail in FIG. 1, which employs in addition to the saturation control winding 305" an auxiliary core schematically represented in FIG. 6 by the corresponding bias-flux or it may be brought about by a high permeability slab 306 in addition to the saturation control winding 305", FIG. 6, which is like that shown in more detail in FIG. 3. Whatever saturation control elements are used for this embodiment it is essential that the magnetic core 300* be locally saturable at the junctions of cores 302 with core 301.

A selector switch 310 is provided which includes wiper arms 311-322 inclusive, which are associated with contact groups 331-342 inclusive. One lead of each of the magnetic control windings 305 is connected to negative battery and the other lead of each is connected to one of the contacts 331 of the switch 310. The leads terminating on contacts 331 of switch 310 are then multipled or paralleled to each of the contact groups 332442 respectively. In the drawing only two of these contact groups, namely 331 and 342, are shown. It is to be understood that other types of selective energizing circuits may be used with this magnetic switching device. The applicant does not desire to be limited to the particular switching arrangement disclosed above and shown in FIG. 6.

Assuming that a flux is introduced in core section 301 and further assuming that none of the magnetic control windings 305 are energized, it will readily be apparent that the flux will remain in core section 301 and will not traverse any of the small core sections 302. Upon the energization of one or more of the control windings 305, a portion or portions of core section 301 Will become saturated, thereby increasing the reluctance of these portions and causing the flux to seek a path around them, which path will be through the small core sections 302 associated with the energized control windings 305. Hence, it can readily be seen that the subscriber stations coupled by windings 303 to the core sections 302 associated with the energized control windings 305 will be magnetically coupled to the flux assumed to be flowing in the circuit. By selective operation of the selector switch 310, it is therefore apparent that any number of the subscriber stations may be magnetically coupled to each other through core section 301 to permit a conference circuit arrangement. The assumed flux may be established by the windings 305 due to their energization by equipment, not shown, included in the subscriber stations. Another method would be to introduce flux into the circuit via another winding linking core section 301, and modulate this flux by audio signals in windings 305.

It is to be understood that numerous modifications in the details of construction and the combination and arrangements of parts may be resorted to without departing from the true spirit and scope of the invention as defined in the following claims.

What is claimed is:

1. A magnetic switching device comprising a core having a common core section forming a closed magnetic path and having a plurality of individual core sections each forming a loop extending from the respective segment of said common core section so that each of said individual core sections is magnetically shunted by a different segment of said common core section; a multiplicity of windings wound on said core at least certain ones of said windings being separately Wound on corresponding ones of said individual core sections; and apparatus for coupling together selected ones of said windings, said apparatus comprising means for selectively saturating said segments so that the magnetic flux in said common core section is diverted through the corresponding individual core section and thereby selectively linked with the winding on the last-mentioned individual core section.

2. A magnetic switching device as claimed in claim 1, and including a winding on said common core section, said selective saturating means causing a selected one of said loop windings to be magnetically coupled to said winding on the common core section.

3. A magnetic switching device as claimed in claim 1, wherein said windings are connected to telephone lines.

4. A magnetic switching device as claimed in claim 1, wherein said saturating means comprises a saturating Winding imbedded in each said segment and Wound in a plane parallel to the path of said magnetic flux so that the saturating'flux is substantially orthogonal to said magnetic flux.

5. A magnetic switching device as claimed in claim 1, wherein said saturating means comprises a saturating winding for setting up a saturating flux orthogonal to said magnetic flux, in each said segment, and a control core intersecting each said segment of said common core section substantially at right angles, so that lines of force of said saturating flux pass orthogonally through said segment and around said control core.

6. A magnetic switching device as claimed in claim 1, wherein said saturating means for each of said segment-s comprises a saturating winding imbedded in a slab of magnetic material having a higher permeability than the material of said magnetic core, said slab being inserted in an air gap in said segment with a close fitting relation between said slab and said segment.

7. A magnetic switching device as claimed in claim 2, wherein said saturating means comprises a permanent magnet, means for moving said magnet relative to and in close proximity to said segments of said common core sec- 8 tion so that a selected one of said segments may be 10- cally saturated 'by the magnetic field of said magnet, thereby magnetically coupling'the winding on the adjoining loop core section with the winding 'on said common core section.

8. A magnetic switching device as claimed in claim 7, wherein said magnet is of a generally U-shaped form and is positioned so that the open-end of said magnet loosely embraces a segment of said common core seection.

9. A magnetic switching device as claimed in claim 1, wherein said common core section has a substantially toroidal form and wherein said plurality of individual core sections are in the form of mutually separate annuli, said plurality of annuli being disposed peripherally around and extending from said common core section.

10. A magnetic switching device as claimed in claim 1, wherein said saturating means comprises a saturating winding wound in a plane orthogonal to said magnetic flux, so that the saturating flux is substantially parallel to said magnetic flux.

References Cited in the file of this patent UNITED STATES PATENTS 2,519,426 Grant Aug. '22, 1950 2,740,110 Trimble Mar. 27, 1956 2,935,622 Crane May 3, 1960 3,017,617 Quade Jan. 16, 1962 FOREIGN PATENTS 755,656 Germany Feb. 23, 1953 1,015,855 Germany Sept. 19, 1957 

